Added EOPNOTSUPP and better error handling in accept.

include/errno.h

@@ -102,6 +102,7 @@ extern int errno;		  /* place where the error numbers go */
 #define EMSGSIZE      (_SIGN 73)  /* Message too long */
 #define ENOTSOCK      (_SIGN 74)  /* Socket operation on non-socket */
 #define ENOPROTOOPT   (_SIGN 75)  /* Protocol not available */
+#define EOPNOTSUPP    (_SIGN 76)  /* Operation not supported */
 
 /* The following are not POSIX errors, but they can still happen. 
  * All of these are generated by the kernel and relate to message passing.

lib/ansi/errlist.c

@@ -85,6 +85,7 @@ const char *_sys_errlist[] = {
 	"Message too long",		/* EMSGSIZE */
 	"Socket operation on non-socket", /* ENOTSOCK */
 	"Protocol not available",	/* ENOPROTOOPT */
+	"Operation not supported",	/* EOPNOTSUPP */
 };
 
 const int _sys_nerr = sizeof(_sys_errlist) / sizeof(_sys_errlist[0]);

lib/ip/accept.c

@@ -23,15 +23,30 @@ int accept(int socket, struct sockaddr *_RESTRICT address,
 	socklen_t *_RESTRICT address_len)
 {
 	int r;
+	nwio_udpopt_t udpopt;
 
 	r= _tcp_accept(socket, address, address_len);
-	return r;
+	if (r != -1 || (errno != ENOTTY && errno != EBADIOCTL))
+		return r;
 
-#if DEBUG
+	/* Unfortunately, we have to return EOPNOTSUPP for a socket that
-	fprintf(stderr, "accept: not implemented for fd %d\n", socket);
+	 * does not support accept (such as a UDP socket) and ENOTSOCK for
-#endif
+	 * filedescriptors that do not refer to a socket.
-	errno= ENOSYS;
+	 */
-	return -1;
+	r= ioctl(socket, NWIOGUDPOPT, &udpopt);
+	if (r == 0)
+	{
+		/* UDP socket */
+		errno= EOPNOTSUPP;
+		return -1;
+	}
+	if ((errno == ENOTTY || errno == EBADIOCTL))
+	{
+		errno= ENOTSOCK;
+		return -1;
+	}
+
+	return r;
 }
 
 static int _tcp_accept(int socket, struct sockaddr *_RESTRICT address,